(1) Field of the Invention
The present invention relates to a drilling jig for a utility pole. In particular, the invention can be used to accurately and efficiently drill a plurality of equally spaced angled holes into a utility pole to facilitate penetration of a preservative into the pole.
(2) Description of the Prior Art
Wooden utility poles are used worldwide to carry overhead cables for electric, telephone and cable TV services. About 130 to 160 million poles are currently in use in the United States alone. These poles may have an average service life of 30 years. Commonly, utility poles are put into the ground about 5 feet. After the first 20 years, poles are inspected at ground level for rot, and are treated, thereby extending the life of the pole. Poles are most susceptible to decay near the ground-line. To prevent decay, sometimes a xe2x80x9cground-line bandagexe2x80x9d can be prepared with pentachlorophenol and grease and wrapped around the post. Alternately, chloropicrin or metam-sodium can be injected into drilled holes, which are then plugged with dowels.
U.S. Pat. No. 6,237,305 to Landers teaches a method for in-situ treatment of wood utility poles. Lander""s process involves excavating an area around the base of a wood pole supported in the earth and drilling a plurality of holes in the wood pole for injecting an isophorone containing compounds into the pole. A preselected coating is used to coat a portion of the pole adjacent the excavated area with a preselected compound containing an isophorone solvent and then covering the coated portion of the pole with a covering wrap prior to refilling the excavated area around the wooden pole for treating the pole in-situ for preventing decay.
Until the present invention, there has not been any efficient method or apparatus suitable for drilling an array of holes necessary for a complete ground-line preservative treatment of a wooden utility pole. What is needed is an apparatus that can align a drill at an individual location within a plurality of locations on a utility pole making it possible to bore an array of accurate treatment holes in a quick and efficient manner.
The present invention is directed to a drilling jig for drilling an array of holes into a utility pole to facilitate the penetration of a preservative, thereby preventing rotting of the pole at ground level. The drilling jig comprises a plate having parallel topside and underside planar surfaces, an upper edge, a lower edge, a first side edge and a second side edge. The plate is generally rigid and can be made from rigid materials such as, but is not limited to metal, wood, plastic, fiberglass, carbon fiber, Kevlar or composite materials. Aluminum has been found to be a particularly useful material for constructing the drilling jig of the present invention, due to its low cost, machineability, durability and light weight.
The plate further includes a set of through-bore guide holes for guiding a drill bit into a utility pole. Preferably, the set of through-bores is arrayed in a rectangular pattern having top and bottom rows, inside rows and outside columns located such that a handheld drill can be guided to drill spaced holes within a predetermined distance of outer-surface of the largest diameter pole to be drilled. Furthermore, the angled drill bit guide holes are spaced at an equidistance of each other and extend through the plate. The through-bores can have a diameter between a range of xc2xc inch and xc2xd inch. Moreover, the array of through-bore guide holes should be longitudinally dimensioned such that a rectangular pattern of holes can extend at least four feet above and below the ground-line of the pole being drilled. The length and width of the plate is dimensioned to accommodate the array of through-bores. However, the length and width of the plate can be of increased proportions to accommodate other preferable members of the drill jig such as guide arms, lashing attachment points, spacer bars and handholds.
The thickness of the plate is such that each through-bore has an axial length sufficient for guiding a handheld drill to drill a hole in a utility pole substantially within ten degrees of perpendicular of the plate""s planar surfaces. It is preferable that the array of holes resulting from the use of the present invention, slope downwardly towards the ground end of the drilled pole. The downward slope of the holes provides drainage preventing water from standing inside the drilled holes for long periods of time. It has been determined that holes sloping downward at an angle between the range of three to ten degrees from perpendicular the longitudinal axis of the drilled pole provide good drainage. Moreover, a level can be included as a member of the drill jig to orient the drill jig into an optimal position for drilling.
An additional feature included with the drilling jig is a number of spacer bars fixed to the underside surface of the drill jig plate. The spacer bars hold the drill jig plate far enough off the surface of the pole being drilled to allow drill shavings to fall away from the holes being drilled. The spacer bars can extend directly from one side edge to the other. One spacer bar can be extended midway between the upper edge and lower edge of the plate separating the drill jig into a below ground-line section that includes the lower edge and an above ground-line section that includes the upper edge.
The drill jig further includes at least one elongated guide arm secured proximal to one of the edges of the plate and extending downwardly transverse the plate. The preferred embodiment includes two guide arms, each secured near the same plate side edge, but substantially separated by distance along the plate side edge with a first guide arm being located in the below ground-line section and a second guide arm being located in the above ground-line section. Each guide arm preferably includes an abutment face for contacting the surface of the pole and for aligning the drill jig into proper lateral position against the sides of the pole being drilled.
Also, at least one lashing member is provided for lashing the drill jig to the utility pole being drilled. Preferably a pair of lashing members is provided. Each lashing member has a first end securable to an attachment point proximal to the drill jig plate""s first side edge and a second end that is releasibly attachable to an attachment point proximal to the plate""s second edge. Moreover, each lashing member can be an element in an adjustable lashing clamp assembly that further includes a tensioning device. Part of the tensioning device can be the second end of the lashing member adapted to adjust the tension of the lashing member.
In the preferred embodiment, the second end of the lashing member consists of a threaded rod integrally attached longitudinally to the end of a chain or cable making up the lashing member. An attachment point is a through-bore with a diameter large enough to accept insertion of the threaded rod.
Each adjustable lashing clamp assembly further includes a tensioning knob for increasing or decreasing the tension of its respective lashing member. Each tensioning knob has internal threads matching external threads of the threaded rod of its respective lashing member. When under tension the threaded rod of a lashing member extends through an attachment point to just above the top planar surface of the drill jig plate. A tensioning knob threaded onto the threaded rod applies tension to the lashing member by applying a counterforce against the top planar surface of the plate.
A convenient feature of the drill jig includes oval handhold cutouts large enough for an adult""s palm preferably positioned within the drill jig plate at locations near both side edges. The handhold cutouts can be used to manually position the drill jig on a utility pole to be drilled.
In operation, users of the drill jig begin the drilling process by supporting the ground end of a utility pole above ground surface, preferably positioning the pole in a horizontal position. For example, the ground end of the pole to be drilled can be positioned and supported such that it overhangs the end of a support structure. Next, the drill jig is positioned against the pole such that the longitudinal axis of the drill jig is parallel to the longitudinal axis of the ground end of the pole. The position of the drill jig is adjusted along the longitudinal axis of the pole until the below ground-line section of the plate is below the pole""s ground-line and the above ground-line section of the plate is above the pole""s ground-line. The position of the drill jig is further adjusted until the abutment faces of the guide arms are in contact with the outer-surface of the pole.
Once properly positioned, the drill jig is ready to be lashed to the pole. The first ends of the lashings are secured to attachment points near the first side edge if not already secure. Next, each lashing is passed around pole on the side of the pole opposite the drill jig. Then, the second end of each lashing is releasibly attached to its respective attachment point near the second edge of the drill jig plate. The tensioning device is then adjusted to add tension to the lashings securing the drill jig such that it is held fast to the pole. At this point, handheld drills can be used to drill a properly placed array of holes above and below the ground line of the pole. Each hole in the pole is drilled by placing the drill bit of a handheld drill into a drill jig through-bore and against the pole. The drill is energized and the drill bit is forced into the pole until the bit travels all the way through the pole or until a desired depth hole is created. The drill bit is then removed and placed into another drill jig through-bore. This process is repeated until the desired number and pattern of holes is completed. The drill jig is then removed from the drilled pole by loosening the tensioning device allowing the drill jig to be taken away from the pole.
While the invention is described herein as a jig to be manually placed on a utility pole, it will be understood that the invention also contemplates systems in which the jig is positioned on the utility pole by powered mechanisms. In such mechanisms, the drill bit or plurality of drill bits, which are guided by the holes in the jig, may be inserted and driven by a powered drive mechanism, instead of by a hand drill operated by an individual.
For example, the jig may be carried on a movable, e.g., hydraulic, arm movable to an operative position to place the jig against the surface of a utility pole. A plurality of bits rotatable by a suitable drive mechanism can then be positioned to align the bits with the holes in the jig, with the bits being extended through the holes and through the utility pole as the bits are rotated. In this configuration, the arm will serve as a positioning member to position the plate relative to the utility pole.